Dual pump arthroscopic irrigation/aspiration system with outflow control

ABSTRACT

A dual pump irrigation/aspiration pump system capable of operating in a plurality of different modes suitable for a variety of different endoscopic surgical procedures. The system monitors actual or calculated intra-articular pressure and adjusts flow to maintain surgeon requested pressure at the surgical site while controlling outflow. The irrigation/aspiration pump system has an inflow pump and tubing dedicated to communicating fluid to the surgical work site and an outflow pump and tubing dedicated to removing fluid from the work site at a controlled rate. The system further has different size inflow and outflow pumps and tubing cassettes, means for altering the outflow fluid flow rate to accommodate a surgical tool and a means for declogging the surgical tool in the event of blockage. In a preferred embodiment a pressure control system provides inferred pressure information representative of the pressure at the work site.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to systems for the irrigation and/or aspiration offluids into or from a surgical work site during an endoscopic procedure.More particularly, the invention relates to a multi-purposeirrigation/aspiration system for use during minimally invasive surgeryfor the purpose of performing any one of a variety ofirrigation/aspiration functions such as, for example, tissue lavage,joint distension or uterine distension. Still more particularly, theinvention relates to an irrigation/aspiration system having a commoncontrol system operating two separate pumps, one pump dedicated toirrigation and one pump dedicated to aspiration. Still more particularlythe invention relates to controlling the outflow fluid when anaspirating surgical tool is used with the system.

2. Description of the Prior Art

Minimally invasive surgery, also referred to herein as endoscopicsurgery, often utilizes an irrigation system to force suitablebiocompatible fluid into the area surrounding the surgical work sitewithin a patient. The term “irrigation” is used broadly to mean any typeof pressurized fluid flow whether it be for irrigation in particular orfor other uses described below. Flexible plastic tubing is used toconduct the fluid from a source to the work site and from the work siteto a drain or other receptacle. Flexible tubing is also sometimes usedas a pressure monitoring line to convey fluid pressure information to acontrol mechanism. Depending upon the procedure, the irrigating fluid isuseful for various purposes such as tissue lavage, hydro-dissection,joint distension, uterine distension, etc. Known irrigation systemsinclude electrically driven pump systems, in which a suitable fluid ispumped through flexible tubes from a source to the work site,gravity-feed systems, in which the pump is replaced by merely adjustingthe height of the fluid supply above the patient, and nitrogen poweredsystems.

Irrigation systems generally utilize a means to set the pressure desiredat the surgical work site. A feedback loop uses information from apressure sensor to maintain the set pressure within a desired range. Theinvention described herein includes improvements in pressure control.

Known aspiration systems employ a source of reduced-pressure (i.e. lowerthan that of the work site) and include vacuum systems, in which avacuum source is simply connected via flexible tubes to the work site,and simple gravity controlled drain lines. Aspiration of the fluidserves to either simply remove it to improve visibility, preventundesirable fluid accumulation or high pressure at the work site, or toregulate the flow rate to maintain a predetermined fluid pressure at thework site.

Because the irrigation and aspiration functions are commonly usedtogether, prior art irrigation/aspiration systems have been developed toperform both functions with one system, often combined in one consolewhich provides power and control. The irrigation system is generallyused in conjunction with an aspiration system which removes the fluidpumped into the work site at a controlled rate depending on the flowrate selected by the surgeon. Dual pump irrigation and aspirationsystems are known where one pump is dedicated to the irrigating functionand another pump is dedicated to the aspirating function. Each systemutilizes a collection of flexible tubes to connect the fluid and vacuumsources to appropriate instruments inserted into the body. Thecollection of tubes includes a fluid inflow conduit, a fluid outflowconduit and, in some instances, a pressure monitoring conduit. All ofthe tubes are packaged together as a tubing set and each tubing set isproduced as a unit containing all necessary tubes and connectionsrequired for performing a particular procedure with a particular system.This invention relates to improvements in dual pumpirrigation/aspiration systems.

Consequently, it is an object of this invention to produce anirrigation/aspiration system having an inflow pump and an outflow pumpand a control system for operating each pump in accordance withpredetermined characteristics defined for use during a selected one ofseveral different surgical procedures.

It is also an object of this invention to produce a multi-purposeirrigation/aspiration system capable of operating with a variety ofspecific types of tubing sets, each set intended for use only during aparticular type of surgical procedure.

It is also an object of this invention to produce a multi-purposeirrigation/aspiration system capable of operating with a variety ofspecific types of tubing sets which are each identified with aparticular coding means associated with that tubing set type to identifythe use for which the tubing set and/or the system associated therewithis intended.

It is also an object of this invention to produce two tubing cassettesfor use with a multi-purpose irrigation/aspiration system wherein onecassette is dedicated to and facilitates the engagement of theirrigation tubing with the system and the other cassette is dedicated toand facilitates the engagement of the aspiration tubing with the system.

It is still another object of this invention to produce a dual pumpirrigation/aspiration system having a flow control system whichautomatically changes the outflow of fluid based on whether anothertool, such as a shaver blade handpiece is activated to withdrawadditional fluid from a surgical work site.

It is yet another object of this invention to produce a dual pumpirrigation/aspiration system having varying size peristaltic rollers andassociated tubing cassettes to facilitate proper assembly.

It is also an object of this invention to produce a dual pumpirrigation/aspiration system having a flow control system capable ofcontrolling selectively pressure and flow on the basis of actualintra-articular pressure or a calculated/inferred pressure.

It is also an object of this invention to produce a dual pumpirrigation/aspiration system having a valve means and a control for thevalve means capable of drawing outflow fluid from selected outflowtubes.

It is yet another object of this invention to produce a dual pumpirrigation/aspiration system having a software driven decloggingfeature.

SUMMARY OF THE INVENTION

These and other objects of this invention are achieved by the preferredembodiment disclosed herein which is a dual pump multi-purposeirrigation/aspiration pump system. The system is designed with a firstpump to pump fluid from a source of irrigating fluid and a second pumpto provide a source of aspirating vacuum during an endoscopic surgicalprocedure at a surgical work site. The system comprises a common consoleand a pump flow control system for controlling both a peristaltic inflowpump and a peristaltic outflow pump. The flow control system utilizesinflow and outflow pressure sensors and inflow and outflow flow ratecontrols. A tubing set comprising an inflow cassette housing, an outflowcassette housing and a plurality of flexible conduits is used to connectthe source of irrigating fluid and aspirating vacuum to the surgicalwork site. The tubing set contains inflow and outflow pressuretransducers and connects them to pressure sensors in the console. Thetubing set is adapted for use during a predetermined type of surgicalprocedure and contains a coding means which carries a code to identifythe type of surgical procedure and selected predetermined fluid pressureand flow characteristics associated therewith. Decoding means isprovided on the console for reading the coding means to determine thecode. Retention means is provided for receiving and holding the tubingcassettes and operatively engaging them and portions of the flexibleconduits with their respective (inflow or outflow) pump, the flow ratecontrol means and the decoding means. Also provided is a control meansresponsive to the code and the pressure sensors for controlling theinflow and outflow fluid pressures and flow rates in accordance with thepredetermined characteristic identified by the code.

A further aspect of this invention is embodied in a system using twotubing cassettes, each for use with a respective one of theirrigation/aspiration pumps accessible on a single power/controlconsole. The tubing cassettes comprise an inflow cassette housing whichholds a first flexible tube for supplying irrigation fluid from a fluidsource to the surgical work site and an outflow cassette housing whichholds a second flexible tube for communicating a vacuum created by theoutflow pump to the surgical work site. Additionally, the cassettes mayalso be provided with pressure transducers for communicating pressuredata from inflow and outflow pressure transducers to pressure sensors onthe console. The cassette housings for receiving the tubes comprise acode carrying means. The tubing cassettes are adapted to automaticallyalign predetermined parts of the housing, code means and tubes withassociated parts of the system console.

In one aspect of this invention a fluid pump system is provided forsupplying fluid to and removing fluid from a surgical site, the systemcomprising a first peristaltic pump for supplying fluid, the firstperistaltic pump having a roller assembly of a first predetermineddiameter, and a second peristaltic pump for removing fluid, the secondperistaltic pump having a roller assembly of a second predetermineddiameter, the second predetermined diameter not equal to the firstpredetermined diameter.

Another aspect of this invention is an improvement in a fluid pumpsystem which has a first fluid pump for pumping fluid from a source to asurgical site and a second fluid pump for removing fluid from thesurgical site at a first predetermined rate wherein the fluid pumpsystem intermittently operates in conjunction with a surgical toolwhich, when operational, removes fluid from the surgical site at asecond predetermined rate greater than the first predetermined rate. Theimprovement comprises a sensor for sensing a predetermined parameter ofthe surgical tool and providing an output signal indicating that thesurgical tool is operating. The improvement further comprises anactuating means responsive to the output signal to actuate the secondfluid pump to remove fluid from the surgical site at secondpredetermined rate.

Another aspect of this invention is an improvement in a fluid pumpsystem which has a first fluid pump for pumping fluid from a source to asurgical site and a second fluid pump for pumping fluid from thesurgical site to a fluid drain and for removing fluid from the surgicalsite at a first predetermined rate, wherein the fluid pump systemintermittently operates in conjunction with a surgical tool which, whenoperational, removes fluid from the surgical site at a secondpredetermined rate greater than said first predetermined rate. Theimprovement comprises a first input tube joining the surgical site tothe second pump and a second input tube joining the surgical tool to thesecond pump and a shuttle means for alternatively pinching one or theother of the first and second input tubes, or neither tube. The shuttlemeans comprises a movable pinching member, moving means for moving themovable pinching member between a first position in which neither of thefirst or second tubes is closed, a second position in which only thefirst input tube is closed and a third position in which only the secondinput tube is closed. The improvement also comprises a control means forsensing the position of the moving means and for producing signalsalternatingly representing the first, second and third positions.

Another aspect of the invention is a method for determining the pressureat a surgical work site in a variety of ways. Various pressure datasources are provided and a selected source is used in the feedbackcontrol loop to maintain the set pressure within a predetermined range.The system determines which pressure data sources are available andcompares data to determine reliability of the data before selecting thepressure data source to be used. More specifically the inventionincludes a method for determining the pressure at a surgical work siteduring an endoscopic surgical procedure utilizing a fluid inflow pump,inflow tubing and an inflow cannula for conveying fluid from a fluidsource to the surgical work site and a fluid outflow pump, outflowtubing and an outflow cannula for conveying fluid from the work site toa drain. The method further utilizes a pressure feedback control loopintended to maintain fluid pressure at the surgical work site at apressure set point by determining actual pressure at the surgical worksite and adjusting pressure and flow parameters to maintain the actualpressure at or near the set point pressure. The method comprises thesteps of providing a first pressure determining means comprising apressure sensor near the inflow pump to measure actual pressure at theoutput of the inflow pump; selectively providing a second pressuredetermining means comprising a pressure sensor at the surgical work siteto measure actual pressure in the joint and providing a third pressuredetermining means comprising a joint pressure inferring system tocalculate the actual pressure at the surgical work site using known andmeasurable pressure and fluid flow characteristics. The method furthercomprises selecting either the first, second or third pressuredetermining means as the source of the actual joint pressure to be usedin the feedback control loop. The method may include the step ofdetermining if a signal indicative of pressure is present at thesurgical work site and, if so, using such signal to control operation ofthe pump.

In yet another aspect of the invention the irrigation/aspiration systemis provided with a means for declogging a surgical tool which may suffera blockage. More specifically, this declogging feature is includedwithin a fluid pump system having a first fluid pump for pumping fluidfrom a source to a surgical site and a second fluid pump for removingfluid from the surgical site at a first predetermined rate. The fluidpump system intermittently operates in conjunction with a surgical toolwhich, when operational, removes fluid from the surgical site at asecond predetermined rate greater than the first predetermined rate. Thedeclogging feature comprises the method of removing a blockage in theoutflow fluid path of the surgical tool wherein the method comprises thesteps of producing a declogging signal, communicating the decloggingsignal to the fluid outflow pump to thereby cause the pump to reverseflow direction for a predetermined period of time and subsequently toreturn to operation in the forward direction for a differentpredetermined time. During the period of reversed flow, the surgicaltool may be withdrawn from the work site so the clog may be directed toa waste container.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front elevation view of a dual pump irrigation/aspirationconsole constructed in accordance with the principles of this invention.

FIG. 2 is a schematic view of the tubing set for use with the console ofFIG. 1.

FIG. 3 is a view of the console of FIG. 1 assembled with the tubing setof FIG. 2 and connected for use during an arthroscopic procedure.

FIG. 4A is a schematic diagram of the shaver sensor component of thesystem.

FIGS. 4B and 4C are top and bottom perspective views of the shaversensor shown schematically in FIG. 4A.

FIG. 5 is a cross-sectional view of FIG. 1 taken along the line A-A andomitting certain components for clarity.

FIG. 6 is a front perspective view of a slidable shuttle valve member.

FIG. 7 is a rear perspective view of FIG. 6.

FIG. 8 is a cross-sectional view of FIG. 1 taken along the line 8-8 withcertain components omitted for clarity.

FIGS. 9 a and 9 b are plan and elevation views, respectively, of FIG. 5showing the components in one particular state of operation.

FIGS. 10 a and 10 b are plan and elevation views, respectively, of FIG.5 showing the components in another state of operation.

FIGS. 11 a and 11 b are plan and elevation views, respectively, of thecomponents of FIG. 5 in yet another state of operation.

FIG. 12 is a bottom perspective view of a portion of FIG. 1 showingportions of the outflow cassette and shuttle valve.

FIG. 13 is a flowchart of a portion of the control system incorporatedinto the console of FIG. 1.

FIG. 14 is a schematic pressure/flow diagram describing variouscomponents of the system depicted in FIG. 3.

FIG. 15 is a flowchart of the declogging procedure portion of thecontrol system used in the console of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to FIGS. 1 and 2 there is shown an exemplary dual pumpirrigation/aspiration system 10 constructed in accordance with theprinciples of this invention and comprising pump console 12 and tubingset 14. Pump system 10 is adapted to deliver irrigating fluid from afluid source to a surgical work site, at a selected pressure and flowrate, in an exemplary set up as shown in FIG. 3. The pump is suitablefor use during a variety of selected surgical procedures and is,therefore, designed to be operable over a wide range of pressure andflow as selected by the user on control panel display 11 by up/downpressure control buttons to set desired pressure and up/down flow ratecontrol buttons to set desired flow. After being set, display 11 canshow actual pressure and/or flow. In the preferred embodiment, thepressure is selectable in 5 mm Hg increments between approximately 0 and150 mm Hg. The inflow flow rate is selectable between approximately 0and 2,500 ml/min (milliliters/minute) in the laparoscopic mode and indiscrete amounts of 50, 100 or 150 ml/min in the arthroscopic mode (withthe outflow flow rate also being 50, 100 or 150 ml/min respectively). Aswill be understood below, the rates may increase when auxiliary devicesare used to remove a greater amount of fluid. Pressure and flow rate areboth controlled by a flow control system incorporated into system 10,the flow control system being microprocessor controlled and menu-driven.Pump console 12 and tubing set 14 serve to communicate fluid from source34 via irrigation or inflow tubing 16 to the work site 18 and from thework site via aspiration or outflow tubing 20 to a drain 22. Pumpconsole 12 comprises an inflow peristaltic pump 30 and an outflowperistaltic pump 40.

Tubing set 14 comprises a plurality of elongated flexible conduits (suchas polyvinyl chloride (PVC) tubes) which are retained in predeterminedrelationships to each other by cassettes 36 and 44 (described below)situated at points intermediate the ends of the various tubes of thetubing set. Tubing cassettes 36 and 44 of the present inventionfacilitate the engagement of the tubing set to the console 12 by holdingintermediate peristaltic roller tubes 50 and 60, respectively, inpredetermined open loop shapes (where the ends of the tubes are attachedto laterally spaced bores on the cassette housings). This enables theuser to easily and one-handedly place the two cassettes into position attheir respective cassette receiving stations on pump console 12. Tubingset 14 is representative of a disposable tubing set usable with pumpsystem 10. Each tubing set may be associated with a particular procedureand may have a differently colored cassettes or cassette labels and eachseparate tube attached to each cassette could be identified by differentcolors or markings to facilitate hooking up the system to the patientand fluid supplies. The different colors or other indicia could indicatethat the code associated with the tubing set causes the system to beprogrammed to automatically limit flow and pressure ranges dependingupon the procedure for which the tubing set is designed.

Tubing set 14 comprising inflow tubing 16 and outflow tubing 20. Inflowtubing 16 comprises inflow tubes 32 a, 32 b and 32 c, inflow cassette 36and inflow tube 38. Tubes 32 a, 32 b and 32 c provide for communicatingfluid from fluid source(s) 34 to inflow tubing cassette 36 attached tothe inflow peristaltic pump 30 and then to inflow tube 38 connected toan endoscope sheath 39 or other appropriate inflow device to communicatethe fluid to the work site 18. Outflow tubing 20 comprises a mainoutflow tube 42, outflow cassette 44, auxiliary outflow tube 72 andoutflow tube 46. Outflow tube 42 is connected to a working cannula 43and is adapted to provide a normal, relatively low flow fluid outflowpath for fluid being aspirated from the work site 18. Auxiliary outflowtube 72 is adapted to provide increased fluid outflow from the work site18 as will be understood below. Both outflow tubes 42 and 72 areconnected to the outflow peristaltic pump 40 as will be understoodbelow.

Inflow tubing 16 further comprises the aforementioned intermediateroller tube 50 (on inflow cassette 36) interposed between inflow tubes32 a and 38. Cassette 36 and roller tube 50 are adapted to engage inflowperistaltic pump 30 at an inflow cassette receiving station 31 on thefront of pump console 12. Outflow tubing 20 further comprises outflowcassette 44 which is adapted to hold the aforementioned intermediateroller tube 60 interposed between outflow tubes 42/72 and 46. Outflowcassette 44 and outflow intermediate roller tube 60 are adapted toengage outflow peristaltic pump 40 at an outflow cassette receivingstation 41. Each cassette 36 and 44 is provided with a pressuretransducer member on its rear surface. Both cassette receiving stations31 and 41 have pressure sensors 75 and 76, respectively, on front panel102 behind cassettes 36 and 44, respectively, as best seen in FIG. 1.The sensors 75 and 76 are adapted to read the pressure when theassociated cassette is properly installed.

The operation and structure of cassettes 36 and 44 and pressure sensors75 and 76 is best understood by reference to U.S. Design Pat. 513,801(Stubkjaer) issued Jan. 24, 2006, U.S. Design 513,320 (Stubkjaer) issuedDec. 27, 2005 and U.S. Ser. No. 10/701,912 (Blight et al.)(PublicationNo. US2005/0095155), filed Nov. 5, 2003, all assigned to the assigneehereof and incorporated by reference herein.

Different Size Pump Heads

Cassettes 36 and 44 facilitate the attachment of tubing set 14 to theinput and output peristaltic pumps 30 and 40, respectively. In thepreferred embodiment the cassettes are further improved over theaforementioned references by making the sizes of certain components onthe inflow side of the system different from the sizes on the outflowside to avoid improper installation of tubing set 14 on pump console 12.Attachment of the tubing improperly could create an unsafe situation.While size variations may be achieved in a variety of ways, in thepreferred embodiment as best seen in FIGS. 1-3 the size of the loopformed by inflow intermediate roller tube 50 is different than the sizeof the loop formed by the outflow intermediate roller tube 60. Therelative sizes of the roller assembly of each peristaltic pump are alsodifferent and adapted to fit on and work with the chosen loop size. Thesize of the inflow and outflow cassettes and the tube lengths, i.e. thedistances along the intermediate roller tubes between the loop ends 36 aand 36 b, and 44 a and 44 b, respectively (i.e. the length of the rollertubes), is varied to assure that cassettes 36 and 44 can only beinstalled one way on their respective receiving station. Furthermore,inflow cassette 36 has a loop length L between the top of theperistaltic roller and the top of cassette 36 when the latter isinstalled at its cassette receiving station. Outflow cassette 40 has asimilarly defined loop length L′ at its receiving station. In thepreferred embodiment the peristaltic rotor (roller assembly) of theinflow peristaltic pump 30 has a diameter (2.89 inches, 73.4 mm), largerthan the rotor of the outflow peristaltic pump 40 (2.45 inches, 62.2mm). The tube lengths of the intermediate roller tubes are chosen toavoid too little tension (i.e. too long a tube) or too much tension(i.e. too short a tube) on the rotor. In the preferred embodiment theinflow and outflow roller tubes 50 and 60 are made of 50A C-Flex® TPEfrom Consolidated Polymer Technologies, Largo, Fla., and each has anoutside diameter of 0.440 inches (11.18 mm), an inside diameter of 0.305inches (7.75 mm), and a wall thickness of 0.068 inches (1.73 mm). Theinflow roller tube 50 is 8.75 inches (222.25 mm) long and the outflowroller tube 60 is 7.25 inches (184.15) long. These dimensions, whenapplied to cassettes having roller to cassette distances of L,approximately equal to 4.36 inches (110.74 mm), and L′ approximatelyequal to 3.54 inches (89.92 mm) enable the cassettes to be properlyinstalled one-handedly onto their respective receiving stations with anacceptable amount of force. In the preferred embodiment the rotors mayalso be color coded to match the proper inflow or outflow cassette tofurther facilitate proper installation. Additionally, the intermediatetubes 50 and 60 may also be color coded.

The loop and rotor size variations of the preferred embodiment haveseveral advantages. Improperly reversing the inflow and outflowcassettes will be almost impossible since placing the larger loop on thesmaller rotor (i.e. inflow cassette on outflow rotor) will not only beapparent to the user but will result in a failure to operate. Theflexible intermediate tube will simply be too loose. Also, placing thesmaller loop on the larger rotor (i.e. outflow cassette on inflow rotor)will also be apparent to the user because the intermediate tube will bestretched too tightly to operate properly, and the force required toplace the outflow cassette on inflow rotor will be so high as to make itnoticeable to the user that something is wrong. It has been found thatthere is a relationship between the force required to properly andeasily place each cassette (using only one hand) at its respectivecassette receiving station. For any given roller tube structure (i.e.diameter, wall thickness, length, etc.) the ratio of tube length to looplength is in the range of approximately 1.7 to 2.1, preferably about1.9.

Shave Sensor and Shuttle Valve

During a surgical procedure a shaver blade handpiece 70 may be usedwithin cannula 43 in conjunction with a shaver blade 73 to resect tissueand otherwise remove debris from the work site 18. The resected tissueand debris are aspirated from the work site 18 along with fluid viacannula 43 and main outflow tube 42. This fluid path is normally openand the fluid flows at a relatively low rate during the surgicalprocedure to maintain pressure at the site and to clear debris. However,when handpiece 70 is operating fluid is made to flow at a higher ratevia auxiliary outflow tube 72. In the preferred embodiment of theinvention, system 10 further comprises a means to identify when shaverhandpiece 70 is operating so that the pump control system canautomatically establish the higher rate of flow. This is accomplished bysensing a predetermined operating parameter of the handpiece and usingthis information to activate a fluid diverter.

As shown in FIG. 3, to use a shaver handpiece a handpiece drive console80 is connected via power line 82 to handpiece 70. In the preferredembodiment a shaver sensor means 84 is used to sense operation of thehandpiece by detecting a parameter associated with the power lineattached to the handpiece. Sensor 84 is connected via signal line 86 topump console 12. As will be understood below, sensor 84 via associatedcircuitry in pump console 12 identifies when the handpiece 70 isactivated and therefore when the fluid flow rate through inflow cassette36 and outflow cassette 44 must increase to compensate for the fluidwithdrawn from the work site by handpiece 70.

As schematically shown in FIGS. 3, 4A, 4B and 4C, sensor 84 is removablymechanically clamped onto power cable 82, preferably near the console 80end in order to place it outside of the sterile field, and includes aresonant circuit/antenna 87, an amplifier, a comparator 88 andoscillator 90. The signal detected by coil 87 is ultimately delivered toconsole 12 on signal line 86 as a frequency output of oscillator 90. Theinput to the oscillator comprises three switches 92, 93 and 94. Switch92 is adapted to provide an input to oscillator 90 on the power-up ofsensor 84 (i.e. connection to console 12). This causes the frequencyoutput of oscillator 90 to be 10 kHz. Switch 93 is adapted to provide aninput to oscillator 90 upon the application of power to power line 82,thus indicating the shaver handpiece 70 is running. This causes thefrequency output of oscillator 90 to be 20 kHz. Switch 94 is adapted toprovide an input to oscillator 90 upon receiving a signal from Hallsensor 95 representative of the presence of magnet 96 near the Hallsensor. Magnet 96 is located in a pivoting clamp 97, one end 98 of whichis movable relative to a base 99 containing the Hall sensor. When theclamp is placed on power line 82 the magnet is no longer detected by theHall sensor (thus leaving switch 94 open). Switches 93 and 94 areadapted to work together to provide a 30 kHz oscillator output. The 30kHz output is used to increase the speed of inflow pump 30 and to turnoutflow pump 40 to the high flow mode and to perform other necessaryfunctions to accomplish this as will be understood below.

An advantage of sensor 84 is its ability to operate with a variety ofshaver systems because it is easily attachable and detachable. Thesensing circuit detects near-field radio frequency (RF) leakage (widespectrum noise) generated by the shaver power line and is, therefore,compatible with all shaver systems (although the method works betterwith AC powered shavers.)

To achieve a high flow mode, in addition to increasing the flow ratethrough inflow cassette 36 the control signal from shaver sensor 84 isused to activate a fluid diverter in the form of a shuttle valve 100,best seen and understood by reference to FIGS. 1 and 5 through 12.Shuttle valve 100 is placed on the front panel 102 adjacent outflowcassette 44 at the point near where outflow tubes 42 and 72 enter amanifold (not shown) on outflow cassette 44. The manifold is an elementhaving two fluid inputs and one common output which serves to join bothtubes 42 and 72 to a common peristaltic outflow intermediate roller tube60. The flow to the input side of intermediate roller tube 60 iscontrolled by passing both of the two fluid input tubes (i.e. outflowtubes 42 and 72) through shuttle valve 100.

Shuttle valve 100 is a pinch valve that operates by alternatinglypinching one or the other of the outflow tubes 42 or 72 closed. Shuttlevalve 100 is accessible on the front panel 102 of pump housing 12adjacent the outflow peristaltic pump 40. As best seen in FIG. 5,shuttle valve 100 is attached to the front panel 102 and comprises ahollow slide housing 104 extending away from front panel 102 andcontaining a sliding shuttle member 106. Housing 104 essentiallyprovides a track within which shuttle member 106 can slidinglyreciprocate. Housing 104 has a central opening 108 wide enough toreceive both outflow tubes 42 and 72 when the outflow cassette 44 isloaded onto its cassette receiving station on the front of the pumphousing 12. Sliding shuttle member 106 includes a central opening 110also adapted to receive both outlet tubes 42 and 72.

The operation of shuttle valve 100 is best understood by reference toFIGS. 8 through 11. In each of these drawings the outflow tubes 42 and72 have been omitted for clarity. It should also be understood thatFIGS. 9A, 10A and 11A are plan views taken along the section line A-A inFIG. 1 while FIGS. 9B, 10B and 11B are front elevation views taken alongthe section line B-B in FIG. 8.

Referring first to FIG. 10A, it is noted that this view is identical toFIG. 5 except for the fact that FIG. 10 a is a view with the outflowcassette 44 in place while FIG. 5 is a view with the outflow cassette 44omitted. Outflow cassette 44 includes a cover tab 120 which is sized tocover openings 108 and 110 in the slide housing 104 and shuttle member106 respectively. Tab 120 supports a backing plate 121 which extendsperpendicularly from tab 120 toward front panel 102. Tab 120 is adaptedto fit between outflow tubes 42 and 72 to facilitate selectivelycovering these tubes. As shown in FIG. 12, housing 104 is a shellgenerally conforming to the shape of shuttle member 106. The hollow baseof housing 104 is notched at slot 123 to provide lateral support for thebottom of the distal end of backing plate 121. Housing 104 may beprovided with a similar slot (not shown) to provide lateral support forthe top of the distal end of backing plate 121.

In FIG. 5 shuttle member 106 is shown within slide housing 104 in acentral position symmetrically situated around housing 104 opening 108which is thereby aligned with shuttle 106 opening 110. As will beunderstood below, this position is automatically presented to the userupon start-up of system 10 in order to facilitate loading of tubing set14. In this central position shuttle member 106 enables outflow cassette44 to be loaded onto outflow peristaltic pump 40, as shown in FIG. 10A,with outflow tubes 42 and 72 both received within opening 110 of shuttlemember 106 and tab 121 situated between the tubes (not shown). As willbe understood below, shuttle member 106 is movable both to the left andright of the central position shown in FIG. 10 a. As best seen in FIGS.6 and 7 shuttle member 106 has a left body member 122 and a right bodymember 124 situated on either side of central opening 110, each member122 and 124 having opposed and inwardly facing pinching surfaces 122 aand 124 a adapted to concentrate a squeezing force on outflow tubes 42and 72, respectively, by alternatively pushing one tube or the otheragainst backing plate 121. Shuttle member 106 has a rear surface 126that can slide along the front panel 102, rear surface 126 having avertical slot 128 at the rear of rear surface 126. Vertical slot 128 isadapted to engage a pin 130 extending through a rectangular slot 132formed in front panel 102. Pin 130 is in turn attached to an arcuate cam134 driven about its axis by a rotatable output drive shaft 136, drivenin turn by shuttle drive motor 140. It will be understood that therotating elements of this mechanism could be replaced by a linearlyreciprocating mechanism or any other suitable device.

FIG. 10B shows the relationship of the components of FIG. 10 a (takenalong the line B-B of FIG. 8 at the point in time represented by FIG.10A). Cam member 134 has a generally semi-circular profile and an outerpartially cylindrical arcuate surface 142 situated at a fixed radiusfrom the axis of drive shaft 136. Surface 142 terminates at oppositeedges 144 and 146. An optical sensor 150, for example a light (or otherradiation) emitting diode situated a predetermined distance from surface142, is focused on surface 142 and adapted to sense the position ofshuttle member 106 in a non-contact manner by detecting the presence andabsence of surface 142 in the field of view of sensor 150. The shuttlemember 106, cam member 134 and sensor 150 are physically correlated sothat a given position of cam member 134 corresponds to define when theshuttle member is centered in the position shown in FIGS. 5 and 10A. Inthe preferred embodiment this correlation is achieved by having theshuttle member 106 in the central position shown in FIG. 10A when edge144 of cam member 134 is situated so as to trigger a signal from sensor150 that arcuate surface 142 cannot be detected. This “no-detect” signalis equivalent to detecting edge 144 and indicates to the control systemthat the shuttle valve member 106 is in its central position therebyindicating that neither of the outflow tubes 42 and 72 is being pinchedor occluded. This is the loading and unloading state of the system whenneither peristaltic pump is operating.

Because of the clockwise direction of rotation of the peristaltic rollerassemblies, the left side of each cassette 36 and 44 is the input sideto its associated pump and the right is the output side of the pump. Theinput of inflow cassette 36 is provided only by single inflow tube 32 c.However, as will be understood below, the input of outflow cassette 44is provided by two sources: outflow tube 42 and outflow tube 72. Asshown in FIG. 2, the exterior surfaces of these tubes may be physicallyjoined to each other and to inflow tube 38 along a predetermined lengthto facilitate installation of tubing set 14. While outflow tubes 42 and72 may be discrete tubes joined along their outer surfaces, they mayalso be a single tube (not shown) having two lumens. Each lumen would ofcourse be joined by a suitable adapter (not shown) where necessary toconnect the lumen to other components. For this reason, outflow tubes 42and 72 are herein sometimes referred to as a dual lumen tube.

The shuttle control system incorporates a self-learning protocol on eachstart-up of console 12. This feature compensates for any reversal of thepolarity of the wiring of motor 140 and determines the home or centerposition where the shuttle valve must be placed to enable loading andremoval of tubing set 14. This feature operates as follows: (1) onstart-up a direction of rotation is arbitrarily selected and voltage ofan arbitrary polarity is applied to motor 140 to drive it to one extremeof motion at which point current to the motor will increase; (2) at thispoint the output of detector 150 is determined (it will be either highor low depending upon whether surface 142 is detected or not); (3) theresults of steps 1 and 2 are correlated in software and the system thus“learns” that whatever extreme position (polarity) resulted from step 1it is thereafter associated with the signal of step 2; (4) the oppositeextreme position (polarity) is therefore automatically associated withthe other possible signal of step 2. The zero, center position is thendetermined by simply reversing direction of the motor until the edge 144crossover is detected.

If at some point in the operation of pump console 12 there is detectedthe operation of an auxiliary device such as handpiece 70 (i.e. via anappropriate signal on line 86), the control system will interpret thesignal from sensor 84 as a requirement to increase flow through shaveroutlet tube 72 (the tube on the right side in FIG. 3 and on the rightside of shuttle opening 110). This will result in a signal to motor 140to move in direction 154 to the position associated with shuttle member106 being in the right-most position as shown in FIG. 11 a. If, however,it is determined desirable to continue drawing fluid from the leftoutlet tube 42 while pinching off the right outlet tube 72 (for examplewhen shaver handpiece 70 is not running so oscillator 90 does notproduce the 30 kHz signal), a signal is sent to motor 140 to rotate cammember 134 in direction 152. This will result in sensor 150 detectingthe presence of cam surface 142, simultaneously moving pin 130 to theleft thereby causing shuttle member 106 to move to the left-mostposition as shown in FIG. 9 b to leave open the left tube while pinchingthe right tube.

Inferred Pressure Sensing System

Pump system 10 utilizes a unique pressure sensing system to control theoperation of inflow and outflow peristaltic pumps 30 and 40. System 10monitors the pressure at the surgical site and increases or decreasesfluid flow through tubing set 14 to maintain the surgeon requestedpressure (i.e. set pressure) at the site while maintaining some outflowto clear debris, etc. from the site. As will be understood below thesystem uses sensed and/or calculated/inferred pressure information toadjust various parameters to maintain set pressure. The pump fluidcontrol system can operate by receiving pressure information from eitherthe inflow cassette sensor 75 alone, both inflow and outflow cassettesensors 75 and 76, or from a separate pressure sensing tube 45 attachedto sensor port 47.

As shown in FIG. 3, tubing set 14 may be set up as a “one-connection”arthroscopic tubing set or as a “two-connection” arthroscopic tubingset. (In a “two-connection set-up, optional tube 45 and pressure port 39b would be utilized, but in a “one-connection set-up they would not beutilized.) The term “one-connection” refers to the number of irrigatingfluid and pressure sensing connections at the work site. Aone-connection tubing set utilizes one fluid inflow line such as tube 38to supply fluid to a work site during a surgical procedure and providespressure information to the pump flow control system within the consolevia a pressure transducer attached to the fluid inflow line andoperative with sensor 75 to produce a pressure value. In this case thepressure transducer is on the back of cassette housing 36 and sensor 75is on front panel 102 adjacent cassette 36. Sensor 75 senses pressure influid tube 38 as described in the aforementioned Publication No. US2005/0095155. As will be understood by those skilled in the art, inarthroscopic procedures, one-connection systems are used with asimplified inflow cannula or scope sheath which does not have a separatepressure sensing port. Alternatively, an optional “two-connection”tubing set could also be used. In this case scope sheath 39 is providedwith a fluid inflow port 39 a and a separate pressure sensing port 39 b.The pressure sensing port 39 b is connected via optional pressuresensing tube 45 to a pressure sensor/transducer 47 on pump console 12. Atwo-connection tubing set provides a way to determine pressure at thework site while a one-connection tubing set determines pressure at agiven point in the fluid path. The pressure at the work site is hereinreferred to as True Intra-articular Pressure (“TIPS”).

Since use of the TIPS system is optional, pump system 10 includes amethod for determining the source of pressure information used to adjustthe fluid flow and pressure produced by the system. Upon start-up, pumpsystem 10 goes through a pressure determination sequence to identify thesource of pressure data. As shown in the flowchart of FIG. 13, pumpsystem 10 first determines at block 200 whether inflow pump 30 isoperating (running) or not (stopped). In either case the sequence ofevents regarding identifying the source of pressure data is the same. Ifthe pressure sensed by the inflow cassette sensor 75 is greater than apredetermined amount, chosen in the preferred embodiment to be 25 mm Hg,the control system will check at block 202 to see if sensor 47 isproducing a signal, thus indicating the optional TIPS line 45 is beingused. If the pressure is under the 25 mm Hg threshold the system willdefault to operating in the “10K” mode, i.e. with measured pressure datacoming from sensor 75. If the measured pressure data exceeds thethreshold and a TIPS signal is detected, block 204 will assure that thepump flow control system will continue to use this TIPS pressure data tocontrol the operation of pump console 12. If no TIPS pressure signal isdetected, block 206 will determine whether to use pressure data from theinflow cassette sensor 75 only (the 10K mode) or from an alternate knownas the Inferred Pressure Sensing (“IPS”) mode. The IPS system will onlybe used as a source of pressure data if (1) there is no TIPS signal atport 47 and (2) there is pressure data at both inflow cassette sensor 75and outflow cassette sensor 76 and (3) there is a difference between thepressures sensed by the inflow and outflow cassette sensors 75 and 76.

The pressure values used by the pump flow control system are monitoredsuch that if the TIPS or IPS pressure data fails or if the TIPS and IPSpressure values are significantly different (e.g. by an order ofmagnitude) the system will revert to the 10K mode for pressureinformation. The pump flow control system is a servo control loop using,as inputs to a proportional integral derivative (PID) comparator, a setpoint equal to the pressure selected by a user on control panel 102 anda feedback signal equal to the actual pressure measured by the system(i.e. from the 10K mode, TIPS or IPS).

The Inferred Pressure Sensing (“IPS”) system is used to indirectlycalculate pressure at the surgical site without measuring pressuredirectly as is done by the TIPS tubing. The IPS system produces apressure value based on sensed pressure and calculated flow at certainpoints in the tubing set and calculating the effect of pressure dropsassociated with certain components of the set. The sensed andcalculated/inferred values are used in various equations to arrive at acalculated value representative of the pressure at the surgical sitewithout having to actually measure pressure at the site. The advantageof this is that it enables the system to provide increased pressuremeasurement accuracy even with a wide variety of cannulas of differentsizes. The IPS system is a method of accounting for fluid flow drops andpressure losses and compensating for these drops and losses to therebymaintain a more accurate pressure at the surgical site.

The mathematical equation describing fluid flow and pressure dropsthrough the various tubes of tubing set 14 is a complex polynomial,although it can be reduced in a first order approximation simply toP=R×F  (equation 1)where R=flow resistance, F=flow rate and P=pressure. This simplifiedexpression is deemed valid because of the magnitude of flow in thesurgical procedures involved (about 1 to 2 liters per minute) andbecause the control system will sample data at very short time intervalsthereby approximating a static system, as will be explained below.

FIG. 3 has been redrawn as a pressure/flow diagram FIG. 14 to explainthe IPS system and the application of the aforementioned equation tothis IPS system. The components of FIG. 3 each have certain pressure,flow and resistance characteristics that are depicted schematically inFIG. 14. Thus, in FIG. 14 the following values are measured by thesystem: P_(in), the inflow pressure sensed by cassette sensor 75associated with the inflow cassette 36; P_(out), the outflow pressuresensed by cassette sensor 76 associated with the outflow cassette 44;F_(in), the inflow fluid flow rate going into the work site 18 asdetermined by an encoder (not shown) adapted to calculate the fluidvolume moved by inflow peristaltic pump 30 per unit of time; andF_(out), the outflow fluid flow rate coming out of the work site asdetermined by a similar encoder (not shown) adapted to calculate thefluid volume moved by outflow peristaltic pump 40 per unit of time.Those skilled in the art will understand that the flow rates can bedetermined as a function of the inner diameter of the intermediateroller tubes, the distance between the rollers of the peristaltic rotorassemblies and the speed of rotation of the rotor assemblies. Thesepressure and flow values are known values which are sampled by thesystem at intervals such as 10 mm (in the preferred embodiment). Theremaining data needed to use the equation P=F×R is the flow resistanceof the tubes and cannulas used in the set-up of FIG. 3.

To facilitate the explanation of FIG. 14 the various resistances areidentified by the name of the component in the flow direction. Thus, theresistance R_(inflow tube) is labeled with the subscript “inflow tube”because it is the resistance of tube 38, the inflow tube encountered bythe fluid after pump 30. This resistance causes a pressure dropP_(drop inflow tube) across the tube. The resistance R_(inflow tube) iscalculated during manufacture of system 10 and stored in memory. Thus,the pressure drop P_(drop inflow tube) across tube 38 is known and=F_(in)×R_(inflow tube). Therefore, the pressure at the inflow port ofcannula 39 (i.e. point 300) can now be calculated asP _(at inflow cannula) =P _(in) −P _(drop inflow tube)which is rewritten asP _(at inflow cannula) =P _(in) −R _(inflow tube) ×F _(in).The fluid flowing through the inflow cannula undergoes a furtherpressure drop before reaching the joint soP _(at inflow cannula) −P _(drop inflow cannula) =P _(joint).We know the pressure drop across inflow cannula 39 isP _(drop inflow cannula) =R _(inflow cannula) ×F _(in).Therefore,P _(at inflow cannula)−(R _(inflow cannula) ×F _(in))=P_(joint)  (equation 2)At this point R_(inflow cannula) is unknown.On the outflow side, we know thatP _(at outflow cannula) =P _(out) +P _(drop outflow tube)andP _(drop outflow tube) =R _(outflow tube) ×F _(out)where P_(out) is the pressure sensed by sensor 76.

Consequently, the pressure at point 302 isP _(at outflow cannula) =P _(out)+(R _(outflow tube) ×F _(out)).

In the preferred embodiment, inflow tube 38 and outflow tube 20 areidentical in length, inner and outer diameter and material compositionand, therefore, R_(outflow tube) is the same as R_(inflow tube). We knowthat the pressure in the joint can be expressed in terms of theparameters at the outflow side asP _(joint) =P _(at outflow cannula) +P _(drop outflow cannula)and thereforeP _(joint) =P _(at outflow cannula)+(F _(out) ×R_(outflow cannula))  (equation 3)We know thatF _(loss) =F _(in) −F _(out)to account for leakage of fluid. Because the data sample rate is fast(in the range of approximately 1 to 20 ms, preferably approximatelyevery 10 ms) we assume no fluid loss so thatF _(in) =F _(out).Therefore, equation 2 may be rewritten asP _(at inflow cannula)−(R _(inflow cannula) ×F _(out))=P_(joint)  (equation 4)

Combining equations 3 and 4 produces the following:P _(at inflow cannula)−(R _(inflow cannula) ×F _(out))=P_(at outflow cannula)+(F _(out) ×R _(outflow cannula))  (equation 5)Rearranging equation 5 results inP _(at inflow cannula) −P _(at outflow cannula) =F _(out)(R_(outflow cannula) +R _(inflow cannula))  (equation 6)In the preferred embodiment the R_(outflow cannula) is very low becauseoutflow cannulas are designed to easily drain fluid from the work site.(As noted below, this explanation requires additional calculations ifthe outflow cannula is restrictive to any appreciable degree.)Additionally, the outflow flow rate is relatively low so the pressuredrop is low. Thus, equation 6 is simplified toP _(at inflow cannula) −P _(at outflow cannula) =F _(out) ×R_(inflow cannula)and R_(inflow cannula) is now able to be determined asR _(inflow cannula)=(P _(at inflow cannula) −P _(at outflow cannula))/F_(out)  (equation 7)R_(inflow cannula) is now known. These results can now be used inequation 4 (since P_(at inflow cannula) is known) to predict thepressure in the joint and regulate the control loop using inflowpressure data. Combining equation 7 and equation 4 results inP _(at inflow cannula)−(R _(inflow cannula) ×F _(out))=P _(joint)P _(joint) =P _(at inflow cannula) −F _(out)[(P _(at inflow cannula) −P_(at outflow cannula))/F _(out)]P _(joint) =P _(outflow cannula)

These results predict the pressure in the joint using outflow pressuredata. The results of the P_(joint) calculation from the inflow side iscompared to the P_(joint) calculation from the outflow side. If there isany difference between the two, outside of a predetermined range, thesystem will revert to a different pressure sensing mode. If the resultsare within the predetermined range, the P_(joint) calculated from theinflow side is used to control the joint pressure. It is noted that thismethod enables calculation of joint pressure through the use ofcalculated values and without the necessity for any direct measurementsof the joint pressure. This solution holds for the simplest case whereall assumptions made above are valid. Further calculations are necessaryto account for a more restrictive outflow cannula than is used in thepreferred embodiment.

Declogging

Pump system 10 also incorporates a declogging method for facilitatingautomatic removal of a blockage of the shaver aspirating tubing line 72.The declogging system comprises software driven steps which control theoutput pump 40 to activate this function.

The declogging feature operates during use of handpiece 70 by sensingvarious characteristics of the operation of system 10 to determine thelikelihood of a clog. If the outflow peristaltic rotor is working andthe inflow peristaltic rotor is not working (or if the inflow rotorspeed is significantly less than the outflow rotor speed) and ifpressure at the work site (or pressure at both cassettes) is notchanging, it is probable that the shaver blade or aspiration line 72 isclogged. In this event, the user may activate a declog button (notshown) which causes the outflow rotor to be activated in the oppositedirection for a time period sufficient to create a pressure pulse tomove approximately 5-15 ml of fluid through outflow line 72, handpiece70 and shaver 73. After this time period the outflow rotor resumesnormal operation. In the preferred embodiment, 5-15 ml of fluiddisplacement is deemed sufficient for the size of the tubing used.Approximately 5 ml of fluid (approximately 6.2 inches (157.48 mm) longin a 0.25 inch (6.35 mm) internal diameter tube) is an estimate of avolume sufficient to move the fluid back to the clog, and anotherapproximately 5 ml is an estimate of the fluid required to push the clogout. In use, the surgeon would remove the shaver from the work site andaim it at a waste container. The declog button would cause the outflowrotor to be run in reverse as quickly as possible for approximatelythree revolutions and then forward for approximately six revolutions topush the clog out.

FIG. 15 is a flowchart describing the operation of the decloggingfeature.

It will be understood by those skilled in the art that numerousimprovements and modifications may be made to the preferred embodimentof the invention disclosed herein without departing from the spirit andscope thereof.

What is claimed is:
 1. A method for controlling a dual lumen outflowtubing set used on a pump housing having a peristaltic pump with a rotorassembly, said method comprising providing said tubing set comprising afirst fluid input tube and a second fluid input tube separated from oneanother by a backing plate, a fluid path of said first fluid input tubebeing joined together with a fluid path of said second fluid input tubeat a location between said backing plate and a common output peristalticroller tube; providing a reciprocating pinching valve member havingopposed pinching surfaces for selectively pinching closed said firstfluid input tube or said second fluid input tube against said backingplate, said pinching valve member movable between a second position andan opposed third position, and having a loading opening between saidpinching surfaces for receiving said first fluid input tube and saidsecond fluid input tube simultaneously with said backing plate;situating said fluid input tubes and said backing plate in said openingof said pinching valve member, said backing plate adapted to be heldstationary in relation to said reciprocating pinching valve member toprovide a surface against which said first fluid input tube may bepinched closed by said pinching valve member in said second position andagainst which said second fluid input tube may be pinched closed by saidpinching valve member in said third position; moving said pinching valvemember to said second position to pinch close said first input tube; andmoving said pinching valve member to said third position to open saidfirst input tube and to pinch close said second input tube.
 2. A methodaccording to claim 1 wherein said pinching valve member is linearlymovable.
 3. A method according to claim 1 wherein said pinching valvemember is arcuately movable.
 4. A method according to claim 1 whereinsaid first and second fluid input tubes are held in a predeterminedposition by a tubing cassette comprising said backing plate and whereinsaid pinching valve member is slidable within a slide housing having anopening adapted to provide access to said loading opening, furthercomprising the steps of: positioning said loading opening adjacent saidslide housing opening to enable said first and second fluid input tubesand said backing plate to be received within said loading opening.
 5. Amethod according to claim 1 wherein said backing plate is part of acassette, which retains said first and second fluid input tubes in apredetermined relationship to each other.